Boron nitride (“BN”) comes in a variety of crystalline structures and has a variety of uses from polishing agents to lubricants. Hexagonal boron nitride (“hBN”) is a very desirable form and a white composition having hexagonal layer structure similar to graphite. Because of its properties, it has found uses in heat conductivity applications, electrical insulation applications, corrosion resistance applications, lubrication applications, and as a plastic additive. Boron nitride can be molded and used in composite materials or as a raw material for cubic boron nitride. It is used in many applications including electronic materials, non-oxidizing ceramics sintering filler powder, makeup materials, medical additives, etc.
BN may be manufactured in a high temperature reaction between inorganic raw materials into a white powder composition of BN particles, having a hexagonal structure similar to graphite in platelet morphology. When platelet BN is added as a filler to a polymer, a blended material is formed having poor rheological properties. At loaded concentrations above 30 wt. % BN, the blended material is so viscous that it is difficult to dispense from a mechanical dispenser such as a syringe.
U.S. Pat. No. 6,731,088 discloses a dry powder of spherically shaped agglomerates of irregular non-spherical BN particles bound together by a binder and subsequently spray-dried. The spherically shaped BN agglomerates can be compounded into polymer compositions at levels of 35-50 wt. % for compositions with viscosity below about 300 cp. U.S. Pat. No. 6,652,822 discloses crystalline particles of BN by generating aerosol comprising precursor of BN particles, generating plasma, and directing the aerosol into and out of the plasma hot zone, with BN being spherical in shape with a diameter of about 1-1000 microns.
There is a need for improved BN compositions having improved properties. There is also a need for BN compositions that can be used in large quantities as a filler in applications such as electronic materials, thermally conductive compositions, and the like. It is particularly desirable for improved BN compositions to be manufactured from existing BN stock as in the mixed boron nitride blends of the invention.